AB1021 FACTORS ASSOCIATED WITH FRAGILITY FRACTURE IN PATIENTS WITH SYSTEMIC MASTOCYTOSIS: DATA FROM AN INCEPTION COHORT IN A SINGLE CENTRE
Authors: K. Carpio, F. Skrabski, I. Castrejon, A. Prieto Garcia, J. M. Alvaro-Gracia, T. González
Journal: Annals of the Rheumatic Diseases (2022)

Background Systemic Mastocytosis (SM) is a very rare disease. Most common manifestations are skin related or anaphylaxis, however almost one third of patients may present with concomitant osteoporosis (OP) resulting in fragility fracture (FF) in around 5 -37% of patients affecting lumbar spine (LS) in young men. Alcohol consumption, high serum tryptase level, and low femoral T score have been described as risk factors but there are some discrepancies between studies. 1-2 Objectives Our primary objective was to identify factors associated with FF in patients with SM. Methods We analysed all consecutive patients attending a multidisciplinary clinic up to April 2021 with SM diagnosis according to the 2001 WHO criteria. We collected demographic data, general risk factors for OP, cutaneous, bone involvement and laboratory data as serum tryptase level. Bone involvement is defined as densitometric OP (T score ≤ - 2.5) or FF. Normally distributed variables are described as means (SD) and dichotomous variables as number and frequencies. Comparison between patients with and without FF is performed using t-test and Chi 2 when needed. Results Seventeen patients with SM are included in this preliminary analysis. Four patients (24%) presented a FF, all of them vertebral fractures identified by plain radiographies.Two men and two women presented FF, they were older versus patients without FF (Table 1), and without general risk factors for OP. All of them have a high basal serum tryptase and most of them presented other MS symptoms (cutaneous, anaphylaxia). FRAX tool was useful in only one patient to predict FF risk. The two men with FF diagnosis do not met criteria for densitometric OP, specific characteristics for these patients are presented in Table 2. Table 1 Population (N = 17) Without fragility fracture (N = 13) With fragility fracture (N=4) P Male, n (%) 9 (53%) 7 (54%) 2 (50%) 0.89 Age at first symptoms, years, mean (SD) 37.6 (21.1) 33.0 (20.2) 58.1 (10.1) 0.05 Age at diagnosis, years, mean (SD) 47.7 (21.1) 38.8 (20.9) 59.7 (13.1) 0.08 Ever smoker, n (%) 6 (35%) 4 (30.8%) 2 (50%) 0.48 Alcohol, n (%) 2 (11.76%) 1 (7.69%) 1 (25%) 0.34 BMI, mean (SD) 26.5 (4.3) 25.3 (4.0) 30.6 (2.0) 0.02 BMI&lt;19kg/m2, n (%) 1 (6%) 1 (7%) 0 (0%) 0.56 Cutaneous mastocytosis, n (%) 8 (47%) 5 (38.5%) 3 (75%) 0.20 Anaphylaxia, n (%) 8 (47%) 6 (46.1%) 2 (50%) 0.89 Digestive symptoms, n (%) 8 (47%) 7 (53.5%) 1 (25%) 0.31 Basal serum tryptase &gt;11,4 12 (70.6%) 8 (61.5%) 4 (100%) 0.14 Basal serum tryptase, mean (SD) 20.20 (18.33) 10.68 (20.75) 22.85 (7.64) 0.75 General risk factors for OP present, n (%) 5 (29%) 5 (38.5%) 0 (100%) 0.14 Femoral T score, mean (SD) -1.03 (1.22) -3.82 (1.36) -1.86 (1.23) 0.12 Lumbar T score, mean (SD) -1.06 (1.57) -5.27 (1.36) -1.95 (2.08) 0.20 Femoral Z score, mean (SD) -0.34 (1.05) -1.79 (1.44) -0.75 (0.65) 0.39 Lumbar Z score, mean (SD) -0.30 (1.88) -5,38 (1.57) -0.67 (2.96) 0.66 FRAX global fracture, mean (SD) 2.27 (2.52) 2.34 (1.57) 6.83 (7.82) 0.11 FRAX hip fracture, mean (SD) 0.23 (1.01) 0.48 (0.27) 2.1 (1.92) 0.18 Table 2. Characteristics of Fragility Fracture in four patients with Systemic Mastocytosis. Patient Age Gender Localization of FF Severity of Fracture Time to fracture diagnosis Patient 1 65 Male D6,D8,D10,D11, L1 3 Mild2 Moderate 2 years prior SM diagnosis Patient 2 81 Female D4,D8,D12, L1 1 Mild3 Severe 2 years after SM diagnosis Patient 3 65 Female D4,D11 Unknown 2 years prior SM diagnosis Patient 4 42 Male D7,D8,D9,D11,D12, L1,L2,L3,L5 3 Mild3 Moderate3 Severe At time of SM diagnosis Conclusion Twenty five percent of patients present FF (multiple, located in dorsal spine, and without densitometric diagnosis of OP). SM should always be considered in differential diagnosis in the presence of FF, especially in men with no OP or another risk factor associated. References [1]van Doormaal JJ. J Allergy Clin Immunol. 2013;131(5):1429-31 e1 [2]van der Veer E. J Allergy Clin Immunol. 2014;134(6):1413-21. Disclosure of Interests None declared